In the manufacture of some types of rigid pin-populated printed wiring boards, known as backplanes, as many as 10,000 terminal pins are inserted into rows of apertures of each of the boards. The pins electrically engage portions of printed wiring on the boards to provide for connections to external circuits. Typically, the spacing between adjacent apertures on each board is extremely small, such as 0.125 inch.
Each of the pins has slender opposite shank or end portions which extend from opposite sides of the boards. After the pins have been assembled with the board, the board is mounted in a frame where external wiring is wire wrapped to the shank or end portions of the pins on one side of the board commonly referred to as the wiring side. Other printed wiring boards, referred to as circuit packs, have electronic components electrically and mechanically secured thereto and have connectors secured to one end thereof. The connectors of these boards ultimately are inserted over selected ones of the shank portions of the pins extending from the other side of the board, commonly referred to as the component side.
During the insertion of the pins into the apertures of the board using a number of prior known methods and apparatus, some of the pins may be bent undesirably. For example, the most severely bent pins may deviate from an axial centerline by 0.050 inch in any direction. Consequently, adjacent pins which are bent in opposite directions could have a combined deviation swing of 0.100 inch.
Since the component side of the pins are destined for insertion into connectors, and the pins on the wiring side may be wired by an automatic wiring facility, it is important that the pins be axially straight and perpendicular to the plane of the board within an acceptable tolerance. Otherwise, a slightly bent pin on the component side, for example, could be misaligned with its mating aperture in the connector. Then, as the connector is moved into place, the bent pin would engage the face of the connector and would be bent further towards the surface of the board, thereby failing to provide the required electrical connection. Similarly, when the pins are wired by an automatic wiring facility, a bent pin could result in further bending of the pin by the facility, without the pin being wired, and/or jamming or damage to the facility.
Copending application Ser. No. 965,219, filed Nov. 30, 1978, and assigned to the same assignee, discloses an automated system for inserting pins into the board in a straight relationship, but because of inherent resiliency, previously bent pins that are inserted into the board will rebound to a non-straight position upon removal of the pins from the apparatus. Thus, the pins still must be straightened after insertion into the board.
Heretofore, various systems have been proposed for straightening shank or end portions of terminal pins projecting from one side of a board after all of the pins have been inserted in the board. For example, in order to provide for the straightening of pins located in a board on a grid spacing of 0.125 inch as above described, in one known pin straightening system a bar having a single row of pin-receiving apertures is lowered to position upper tip ends of a row of pins into the pin-receiving apertures of the bar. A conical lead-in portion for each aperture of the bar insures that drastically bent pins are received into the pin-receiving apertures. Thereafter, the bar is reciprocated in a plane of the row of pins which is referred to as the "X" direction. As the bar is reciprocated, the tip ends of the pins engage laterally spaced walls of the apertures whereby an upper projecting shank or end portion of each of the pins is flexed and coldworked, and then aligned in the "X" direction. In order to provide sufficient flexing and coldworking of the row of pins in a "Y" direction, a support table for the board then is reciprocated an amount such that upper end portions of the pins of the adjacent rows are bent by the sides of the bar away from the upper end portions of the pins located within the bar.
In order to compensate for this effect, the upper end portions of the pins of the first row of pins to be straightened are purposely not fully straightened in the "Y" direction but are left leaning slightly in the "Y" direction toward the adjacent or second row of pins, which is the next row to be straightened. The bar is then retracted and the support table is indexed in a "Y" direction so that the bar is positioned over the second row of pins, the upper end portions of which are then straightened properly in the "X" direction. Thereafter, the support table is reciprocated in the "Y" direction as above described between the first and a third row of pins.
As noted above, the upper end portions of the pins of the first row have been straightened in the "X" direction but are leaning slightly in the "Y" direction toward the second row of pins, the tip ends of which are now located within the apertures of the bar. As the support table is reciprocated in the "Y" direction, one side of the bar engages the slightly bent upper end portions of the pins of the first row and bends the pins in the "Y" direction so that the upper end portions of the pins are now leaning away from the second row of pins. As the bar moves in the reciprocating motion toward the third row of pins and away from the first row of pins, the upper end portions of the pins of the first row now tend to return to their intial position of leaning toward the second row of pins, but actually only spring to a generally straightened position. After the support table has completed its reciprocating movement in the "Y" direction, the upper end portions of the pins of the second row also are left leaning slightly in the "Y" direction toward the third row of pins. In this way, the upper end portions of the pins of the first row are now generally straight but the upper end portions of the pins of the second row are leaning in the "Y" direction toward the pins of the third row.
This pattern of operation then is continued until the upper end portions of all of the pins of the board have been straightened in the "X" and "Y" directions. The board then may be inverted in the apparatus and the end portions of the pins projecting from the opposite side of the board may be straightened in the same manner.
U.S. Pat. No. 3,779,291 to H. G. Yeo also reveals a pin-straightening machine for straightening simultaneously portions of all of the pins of a multiple-pin board (backplane) projecting from one side of the board, after the pins have been secured to the board. The board-secured pins are simultaneously located in holes of a plate whereafter relative motion is provided between the plate and the board. The motion is timed and controlled as to the amount, direction and sequence of relative motion imparted. Ultimately, axial deformity of any of the pins is corrected.
More specifically, the machine disclosed in the Yeo U.S. Pat. No. 3,779,291 initially requires that the board be positioned so that the pins can be inserted face down through apertures of a fixed plate. Once the pins have been inserted through the apertures of the fixed plate, the tips of the pins are located within apertures of a movable grid plate concealed within an enclosure of an operating table. After the tips of the pins have been inserted into the apertures of the grid plate, a cover is lowered over the upwardly facing side of the board and clamped in the closed position by latches. A resilient facing pad, located on the inner surface of the cover, is positioned in engagement with the upwardly facing side of the board. The grid plate is then selectively moved in a variety of directions to effect the straightening of the pins.
Accordingly, a primary purpose of this invention is to provide a new and improved method and apparatus in which opposite end portions of a row of terminal pins in a board are straightened simultaneously, as the row of pins is inserted into the board.